Document APP_ENV value for installation
Document APP_ENV value for installation

I discovered through trial and error that if `APP_ENV` is not set to `local` when you run `php artisan canvas:install`, the database creation process will hang, but no error will be given. This commit updates the documentation to clarify what the value of `APP_ENV` should be.
foxted/canvas,cnvs/canvas,cnvs/canvas,talvbansal/Canvas,lukio3/theduckone,cnvs/canvas